Dresden 2014 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 58: Multiferroics II (organized by MA)
TT 58.10: Talk
Wednesday, April 2, 2014, 12:00–12:15, HSZ 04
Structure and Magnetic Coupling in YBaFeCuO5 — •Andrea Scaramucci1, Mickael Morin2, Ekaterina Pomjakushina2, Marek Bartkowiak2, Denis Sheptyakov2, Lukas Keller2, Juan Rodriguez-Carvajal3, Michel Kenzelmann2, Kazimierz Conder2, Marisa Medarde2, and Nicola A. Spaldin1 — 1Materials Theory, ETH-Zurich, Zurich, Switzerland — 2Paul Scherrer Institute, Villigen, Switzerland — 3Institute Laue Langevin, Grenoble, France
We theoretically study the structure and exchange couplings in multiferroic YBaFeCuO5 (YBFCO). Using density functional theory we calculate energies of configurations with various Fe3+/Cu2+ orderings in the bilayered perovskite structure of YBFCO. We find that configurations with different distribution of Fe3+ and Cu2+ ions fall into two groups with distinctly different energies. The energies of those in the lowest energy group are close to that of the ground state (relative to the growth temperature) suggesting Fe3+ and Cu2+ to be disordered in YBFCO. Finally, we calculate exchange coupling constants for all the low energy configurations and show that the magnetic ordering resulting from these couplings is compatible with the experimentally-observed high-temperature magnetic ordering. However, they do not explain the existence of the experimentally observed low-temperature incommensurate magnetic structure.